Although cognitive decline is the central feature of progressive degenerative dementias such as Alzheimer's disease, the methods that are used to evaluate cognitive impairment are quite gross and generally reveal only relatively advanced levels of impairment. Early diagnosis of these progressive diseases will depend upon development of much more sensitive and analytic measures of cognition. The research proposed here adopts an information processing approach to the analysis of cognitive skills, using response time tasks that allow basic cognitive operations (e.g., encoding, scanning, response preparation) to be isolated and evaluated. The design of the study will allow us to identify specific areas of deficit in the Alzheimer patient relative to normal controls; in addition, the multiple-testing format will allow us to trace cognitive changes over time in a very sensitive manner. The Cognitive Battery that will be administered, subsequent to the initial neurological and cognitive assessment, will consist of seven response time measures for the evaluation of memory, language, attention, and motor skills. These tasks are designed to identify basic operations within a skill; for example, the recognition memory data will provide a measure of the speed with which memory can be scanned that is independent of encoding and response preparation time. The speed and accuracy of the following cognitive operations will be evaluated: word recognition, orienting of spatial attention, motor speed (finger tapping), learning motor sequences, response preparation (alerting), memory scanning and retrieval, and generation of visual and speech codes. Two groups of subjects, mild Alzheimer's patients and normal controls, will complete these tasks three times, at four month intervals. Each task is designed to reveal efficiency of processing within a single session as well as subtle changes in processing that may occur over time. This response time analysis promises to be a powerful and highly quantitative assay of cognitive functioning and of the specific operations that are affected early in the course of dementia of the Alzheimer's type. The results of this project will be used to evaluate the feasibility of using this approach in differential diagnosis and drug treatment evaluations.